An electrophotographic image forming apparatus uses a developing apparatus (development roller) to develop an electrostatic latent image formed on an electrophotographic photosensitive member, which is in the form of a drum (which hereafter will be referred to as photosensitive drum). Conventionally, electrophotographic image forming apparatuses are structured as follows:
In the case of some conventional electrophotographic image forming apparatuses, a cartridge (development cartridge or process cartridge) is provided with a gear. It is mounted in the main assembly of an image forming apparatus, in such a manner that the gear of the cartridge meshes with a gear with which the main assembly is provided. Thus, the development roller in the cartridge can be rotated by the rotational force transmitted to the development roller from a motor, with which the main assembly is provided, through the gear of the main assembly and the gear of the cartridge (U.S. Pat. No. 7,027,754).
In the case of the conventional electrophotographic image forming apparatuses of the other type, a cartridge is provided with the cartridge portion of the development roller coupling, whereas the main assembly is provided with the main assembly portion of the development roller coupling. Further, the main assembly is provided with a member for moving (forward or backward) the main assembly portion of the development roller coupling so that the main assembly portion of the development roller coupling can be moved forward (toward cartridge) in the axial direction of the coupling to engage the main assembly portion of the coupling with the cartridge portion of the coupling, or backward (away from cartridge) in the axial direction of the coupling to disengage the main assembly portion of the coupling from the cartridge portion of the coupling.
Thus, as the main assembly portion of the development roller coupling is rotated after the proper mounting of the cartridge into the main assembly, the rotational force of the main assembly portion of the development roller coupling is transmitted to the cartridge portion of the development roller coupling, rotating thereby the development roller (U.S. Pat. No. 2007/0,160,384).
However, the conventional structural arrangements described above make it necessary that when a cartridge is mounted into, or removed from, the main assembly of an image forming apparatus in the direction which is practically perpendicular to the axial line of the development roller in the cartridge, the main assembly portion of the developer coupling is moved in its axial direction. That is, when a cartridge is mounted or dismounted, the main assembly portion of the development roller coupling has to be moved in the horizontal direction by the opening or closing movement of the cover, with which the main assembly is provided. That is, the opening movement of the cover main assembly has to move the main assembly portion of the development roller coupling in the direction to separate from the cartridge portion of the development roller coupling, whereas the closing movement of the main assembly cover has to move the main assembly portion of the development roller coupling in the direction to engage with the cartridge portion of the development roller coupling.
In other words, one of the conventional technologies described above makes it necessary for the main assembly of an image forming apparatus to be structured so that the abovementioned rotational member (movable member) is moved in the direction parallel to its axial line by the opening or closing movement of the cartridge cover of the main assembly.
In the case of another conventional structural arrangement, it is unnecessary to move the cartridge driving gear of the main assembly forward or backward in the direction parallel to the axial line of the driving gear at the time of mounting a cartridge into the main assembly of an image forming apparatus, or dismounting the cartridge from the main assembly. Thus, this structural arrangement makes it possible to mount or dismount a cartridge in the direction which is practically perpendicular to the axial line of the cartridge driving gear of the main assembly. In the case of this structural arrangement, however, the portion through which driving force is transmitted from the main assembly to the cartridge is the interface (point of meshing) between the driving force transmitting gear of the main assembly, and the driving force receiving gear of the cartridge, making it difficult to prevent the problem that the development roller fluctuates in its rotational speed.